1. Field of the Invention
The present invention relates to an apparatus and method for displaying test results, and to a recording medium, and in particular, to an apparatus and method for displaying results of a test in which each of a plurality of semiconductor chips formed on a wafer substrate is tested, and to a recording medium on which a display program is recorded.
2. Description of the Prior Art
Conventionally, for example, a predetermined voltage is applied to each of the semiconductor chips formed on a wafer substrate to carry out a test (a probe test or the like) to check whether memories and devices formed on the semiconductor chips are operating in a normal state by checking whether a predetermined voltage value which the chip was designed to exhibit is in fact detected when the predetermined voltage is applied to the semiconductor chips. In this way, the quality of the chips (memories and devices) is checked.
At this time, as shown in FIG. 6, numbers (1-7) indicative of the results of the test of the chips are displayed on a screen in correspondence with the each of positions of the semiconductor chips on the wafer substrate. At the same time, the number of semiconductor chips detected as having a given value (one of 1-7) is displayed on the screen for each of the detected values. These numbers (1-7) indicate the quality level of the semiconductor chips. For example, the number 1 denotes a good quality, 2 denotes a quality that can be made good through a very simple correction processing, 3 denotes a quality that can be made good through a relatively simple correction processing, 4 denotes a quality that can be made good through a complicated correction processing, 5 denotes a device failure (defective device), 6 denotes a memory failure, and 7 denotes a function failure. The quality level is determined every time in accordance with the test contents and the test results.
By summing up such quality level, the quality level (failure level) in which the detected number of the semiconductor chips is large is clarified. The causes of the failure are investigated and the results of the investigation are fed back to the manufacturing step for the prevention of failures for the same reason the next time the product is manufactured.
Generally, in testing semiconductor chips, a wafer prober or the like is used which has a tester having a plurality of groups of probes which are each a test portion for testing one semiconductor chip. The wafer prober is used to carry out parallel measurement for testing a plurality of semiconductor chips at the same time, thereby shorting the test time.
For example, there will be considered a case of a wafer prober in which a tester having sixteen groups of probes arranged in eight rows and two columns is provided. The semiconductor chips formed on the wafer substrate are positioned in rows and columns as shown in FIG. 7. As shown in FIG. 7, the tester is disposed at a test start reference position (the slanted line region of FIG. 7). In the case where a semiconductor chip corresponding to at least one of the sixteen groups of probes of the tester is present, the semiconductor chip is tested by the group of probes corresponding thereto. When the test by the groups of probes is completed, the tester is shifted two rows, and a test region 40 is shifted by two rows. When a semiconductor chip is present which corresponds to at least one of the probes, the semiconductor chip is tested with the group of probes corresponding thereto. When testing of all the semiconductor chips formed at the positions of rows one to eight on the wafer substrate is completed by repeating the aforementioned process, the tester is returned to the test start reference position and is shifted eight columns. Thereafter, testing of the semiconductor chips formed at the positions of rows nine to sixteen on the wafer substrate is carried out as described above.
By repeating such operations, all of the 536 semiconductor chips formed on one wafer substrate are tested by the movement of the tester 48 times (carrying out testing 48 times).
Shortening of the test time is important in terms of improving manufacturing efficiency. Conventionally, there has been proposed a wafer prober that is capable of moving the tester freely in order to carry out testing in a short time. As shown in FIG. 8, there is proposed a system in which the test region 40 can be set in correspondence with the configuration of a disc-shaped wafer substrate by moving the tester along the configuration of the disc-like wafer substrate so that the number of times testing is carried out by the tester is decreased.
In the example shown in FIG. 7, all of the 536 semiconductor chips are tested by carrying out testing 48 times. However, by moving the tester in accordance with the configuration of the disc-shaped wafer substrate, it becomes possible to test all of the 536 semiconductor chips in 44 tests. The time required for testing can thus be shortened by the amount of time required for four tests.
Since the semiconductor chips are very small and the electrodes formed on the semiconductor chips are also considerably minute, the probe for applying voltage to the semiconductor chips by contacting the electrode of the chip is also extremely small. As a result, the probe is liable to be broken if a load is applied to the probe during the movement of the tester, or the probe gets caught on the edge of the wafer substrate.
Accurate test results cannot be obtained from damaged probes. Thus, even a good quality semiconductor chip which is subjected to testing may be detected as being a poor product. Such incorrect test results are unfavorable. Therefore, it is necessary to detect at an early stage the fact that the probe has been damaged, so that adjustments to the semiconductor test device can be made and the test instruments can be checked with a view to restoring normal operation in a short time.
Conventionally, when results of testing the semiconductor chip (the quality levels of the semiconductor chips) are displayed on the screen in correspondence to the positions of the semiconductor chips on the substrate, the relative position of the probe with respect to the tester (hereinafter referred to as DFT (Device For Testing)) is displayed on the screen in an overlaid manner on the test results of the semiconductor chips on the monitor, so that the operator can detect the damage caused to the probe as soon as possible.
With a wafer prober in which the movement of the tester is restricted, for example, as shown in FIG. 7, since each of the DFT""s is shifted (arranged)along the same column on the wafer substrate, the damage on the probe can be detected relatively easily. However, in a case where testing is carried out by using a wafer prober in which the tester is moved freely, for example, as shown in FIG. 8, the respective DFT""s are not necessarily shifted along the same column on the wafer substrate. Thus, it is difficult to detect at an early stage which of the DFT""s is damaged.
Furthermore, in recent years, owing to the smaller sizing resulting from the shrinkage or the like of the semiconductor chips and an increase in the diameter of the wafer substrate, the number of chips which can be formed on a single wafer substrate has become very large. As a result, it becomes difficult to display on one screen of the monitor the test results for one wafer substrate. Therefore, only a portion of the test results for one wafer substrate is displayed on one screen of the monitor. For this reason as well, it is difficult to correspond each of the semiconductor chips being tested by the one of the DFT""s with each of the DFT""s, and thus, it becomes difficult to detect at an early stage which of the probes of the DFT are damaged.
In view of the aforementioned, the present invention aims to provide a method and an apparatus for displaying test results, and a recording medium, which provide easy detection of which of the probe is damaged.
In order to attain the above object, the first aspect of the present invention is a method for displaying test results comprising the step of: on the basis of test results obtained by a tester provided with plural testing portions, each of the testing portions testing a plurality of semiconductor chips formed on a wafer substrate, displaying on a same screen of displaying means two types of information which are a first information which expresses test results of the semiconductor chips in accordance with positions of the semiconductor chips on the wafer substrate, and a second information which expresses test results of the semiconductor chips for the respective testing portions of the tester.
The second aspect of the present invention is a method for displaying test results according to the first aspect, wherein at least two of the two types of information obtained from at least two testers are displayed on the same screen of the displaying means.
The third aspect of the present invention is a method for displaying test results according to the first or the second aspect, wherein a display mode is switchable between at least three display modes which are a first display mode for displaying only the first information on the screen of the displaying means, a second display mode for displaying only the second information on the screen of the displaying means, and a third display mode for displaying both the first information and the second information on the screen of the displaying means.
The forth aspect of the present invention is a method for displaying test results according to any one of the first to third aspect, wherein the test results of the second information is at least one of a detection ratio of defective semiconductor chip and a value reflecting the detection ratio.
The fifth aspect of the present invention is an apparatus for displaying test results comprising: control means for controlling a displaying means such that, on the basis of test results obtained by a tester provided with plural testing portions, each of the testing portions testing a plurality of semiconductor chips formed on a wafer substrate, the displaying means displays on a same screen two types of information which are a first information which expresses test results of the semiconductor chips in accordance with positions of the semiconductor chips on the wafer substrate, and a second information which expresses test results of the semiconductor chips for the respective testing portions of the tester.
The sixth aspect of the present invention is an apparatus for displaying test results according to fifth aspect, wherein the control means is connected to at least two testers, and controls the displaying means so that at least two of the two types of information which are obtained from each of the testers are displayed on the same screen of the displaying means.
The seventh aspect of the present invention is an apparatus for displaying test results according to fifth or sixth aspect, further comprising switching means for switching a display mode between at least three display modes which are a first display mode for displaying only the first information on the screen of the displaying means, a second display mode for displaying only the second information on the screen of the displaying means, and a third display mode for displaying both the first and the second information on the screen of the displaying means.
The eighth aspect of the present invention is an apparatus for displaying test results according to any one of fifth to seventh aspect, wherein the test results of the second information is at least one of a detection ratio of defective semiconductor chip and a value reflecting the detection ratio.
The ninth aspect of the present invention is a recording medium which can be read by a computer, the medium having a display program recorded therein for, on the basis of test results obtained by a tester provided with plural testing portions, each of the testing portions testing a plurality of semiconductor chips formed on a wafer substrate, displaying on a same screen of displaying means two types of information which are a first information which expresses test results of the semiconductor chips in accordance with positions of the semiconductor chips on the wafer substrate, and a second information which expresses test results of the semiconductor chips for the respective testing portions of the tester.
The tenth aspect of the present invention is a recording medium according to ninth aspect, wherein a parallel display program, for displaying in a parallel manner and on the same screen, at least two sets of the two types of information inputted independently from at least two testers, is also recorded on the recording medium.
The eleventh aspect of the present invention is a recording medium according to ninth or tenth aspect, wherein a display switch program, for switching a display mode between at least three display modes which are a first display mode for displaying only the first information on the screen of the displaying means, a second display mode for displaying only the second information on the screen of the displaying means, and a third display mode for displaying both the first information and the second information on the screen of the displaying means, is also recorded on the recording medium.
The twelfth aspect of the present invention is a recording medium according to any one of ninth to eleventh aspect, wherein the test results of the second information is at least one of a detection ratio of detective semiconductor and a value reflecting the detection ratio.
In other words, in the first aspect, two types of information are displayed on the same screen: first information which expresses test results of the semiconductor chips in accordance with positions on the wafer substrate of the semiconductor chips which have been tested, and second information which expresses the test results of the semiconductor chips, each of the chips being tested by one of the plurality of test portions, for each of the testing portions of the tester. Therefore, the operator can confirm by the first information the test results of the semiconductor chips which are formed on the wafer substrate, and can confirm by the second information the test results of each of the test portions. Consequently, it is easy to confirm the presence of abnormalities in each of the plurality of the test portions, so that breakage of and trouble with the test portions can be immediately detected.
Even in the case where the semiconductor chips which should be tested by the tester are randomly selected, by using the display of the second information, it can immediately be detected whether the test results of any of the plural testing portions are abnormal. Thus, it is possible to detect at an early stage breakage of or trouble with the test portions.
In order to realize the method of the first aspect, for example, as described in the fifth aspect, an apparatus for displaying test results may be provided with a control means for controlling the displaying means so that the two types of information (the first information and the second information) are displayed on the same screen.
Furthermore, as described in the second aspect, the results of simultaneously testing semiconductor chips formed individually on each of at least two wafer substrates can be confirmed at one time by displaying on the same screen at least two of the two kinds of information obtained at least from two testers, thereby increasing efficiency.
In order to realize the method according to the second aspect, as in the sixth aspect, the apparatus for displaying test results may be structured such that a control means controls the display means so that at least two of the aforementioned two kinds of information obtained from at least two testers can be displayed on the same screen.
Furthermore, as in the third aspect, it is possible to selectively display only information required by the operator by switching between at least three display modes which are a first display mode for displaying only the first information, a second display mode for displaying only the second information, and a third display mode for displaying both the first and second information.
In order to realize the method according to the third aspect, for example, as in the seventh aspect, the apparatus for displaying test results may be structured so as to further comprise switching means for switching the display mode of the displaying means between at least the three display modes which are the first display mode, the second display mode, and the third display mode.
In this case, as in the second and the sixth aspects, the invention is advantageous in cases where there is a large amount of display information, as in the case where testing of the semiconductor chips formed on each of at least two wafer substrates is carried out simultaneously in a parallel manner.
On the basis of test results obtained by a tester provided with plural testing portions, each of the testing portions testing a plurality of semiconductor chips formed on a wafer substrate, the method for displaying test results of the first aspect and the apparatus for displaying test results of the fifth aspect effect processing on the basis of a display program for displaying on a same screen of displaying means two types of information which are a first information which expresses test results of the semiconductor chips in accordance with positions of the semiconductor chips on the wafer substrate, and second information which expresses test results of the semiconductor chips for the respective testing portions of the tester.
This display program is recorded on a recording medium that can be read by a computer, as in the ninth aspect. Thus, the display program can be applied such that after the display program is installed from the recording medium onto a predetermined region of the apparatus for displaying test results, the apparatus for displaying test results is controlled by the program, or such that the display program is directly read from the recording medium and the apparatus for displaying test results is controlled by the program.
Furthermore, in addition to the display program as in the ninth aspect, the recording medium according to the tenth aspect further includes a parallel display program for displaying in a parallel manner and on the same screen at least two sets of the two types of information inputted independently from at least two of the testers, is also recorded on the recording medium. The apparatus for displaying test results as in sixth aspect carries out processing on the basis of this parallel display program.
This parallel display program can be applied such that after the display program is installed from the recording medium onto a predetermined region of the apparatus for displaying test results, the apparatus for displaying test results is controlled, or such that the display program is directly read from the recording medium and the apparatus for displaying test results is controlled.
Furthermore, in addition to the display program as in the ninth or tenth aspect, the recording medium in eleventh aspect further includes a display switching program for switching the display mode of the displaying means between at least three display modes which are a first display mode for displaying only the first information, a second display mode for displaying only the second information, and a third display mode for displaying the first information and the second information. The apparatus for displaying test results of as in seventh aspect carries out processing on the basis of the display switching program.
The display switching program can be applied such that after the display program is installed from the recording medium onto a predetermined region of the apparatus for displaying test results, the apparatus for displaying test results is controlled, or such that the display program is directly read from the recording medium and the apparatus for displaying test results is controlled.
The test results of the first information may be a quality level of the semiconductor chip that is determined each time in accordance with the test contents and the required test results. Furthermore, the test results of the second information may be actual test results such as the quality level of the semiconductor chips, in the same manner as the first information. However, the second information may be at least one of a detection rate of poor products (defective semiconductor chips) or a value reflecting a detection rate as can be seen in the forth, eighth and twelfth aspects. The setting of the second information in this manner is preferable because abnormalities in the test results of the test portions can be clearly displayed.